The present invention relates to an improved anti-locking system in an auger type ice making machine, which prevents a geared motor from being locked due to an occurrence of freeze-up in an evaporator of the auger type ice making machine.
In an auger type ice making machine, a cooling evaporation tube (hereinafter also referred to as the xe2x80x9cevaporatorxe2x80x9d) is wound around an outer peripheral surface of a cylindrical refrigeration casing (hereinafter also referred to as the xe2x80x9ccylinderxe2x80x9d). Mounted within the cylinder is an auger disposed coaxially with, and rotatably around, the longitudinal axis of the cylinder. The auger has a helical blade formed thereon. On the other hand, water to be used for an ice making process (hereinafter referred to as the xe2x80x9cwater to be frozenxe2x80x9d) supplied into the cylinder from a supply pipe disposed in a lower part of the cylinder, is frozen into ice on an inner peripheral surface of the cylinder. The ice crystals thus formed are scraped off the cylinder inner surface by the helical blade of the auger that is rotationally driven by a gear motor, and are carried upward within the cylinder due to a feed-screw action, to be compressed by a compressing head and severed by a cutter to produce chipped ice.
However, ice making capacity of this auger type ice making machine is affected by such factors as ambient temperature and water temperature. Accordingly, generation of an abnormally large amount of ice within the cylinder may lead to a phenomenon in which the generated ice plugs the interior portion of the compressing head to cause locking of the gear motor that drives the helical blade. Various measures have been devised to prevent such a phenomenon.
One example of an auger type ice making machine adapted to overcome this problem is disclosed in JP 60-042567 A. As shown in FIG. 8, in the auger type ice making machine disclosed therein, an auger 3 having a helical blade formed thereon is mounted within a cylinder 1 such that it is rotationally driven by a driving apparatus 4 (motor). An evaporator 5 is wound around an outer peripheral surface of the cylinder 1. Refrigerant is supplied to this evaporator 5 from a refrigeration circuit composed of a compressor 6, a condenser 7, and an expansion valve 8, whereby the water to be frozen supplied from a supply pipe 9 is frozen into ice on the inner peripheral surface of the cylinder 1. A temperature sensing device 10 is disposed at the outlet of the evaporator 5. When the temperature sensing device 10 senses an impending occurrence of freeze-up due to an abrupt drop in the temperature within the evaporator 5, a three-way valve 11 is opened whereby a high-temperature refrigerant from the compressor 6 is introduced into the evaporator 5 through a bypass passage 12. Accordingly, the ice frozen in excess within the cylinder 1 is allowed to melt, thus preventing the driving apparatus 4 from being locked.
Further, in the case where a gas thermometer is used as the temperature sensing device 10 provided at the outlet of the evaporator 5 being on the low-pressure side, the temperature sensing device 10 judges, upon sensing the evaporator temperature, whether or not freeze-up is occurring within the evaporator 5 and an ice making operation is completely halted if freeze-up is judged to be occurring, thereby preventing the auger type ice making machine from being locked.
However, in the conventional ice making machine described above, a normal ice making operation is not performed while the high-temperature refrigerant is being introduced into the evaporator 5 though the bypass passage 12. That is, a normal ice making operation is temporarily halted during this period, which means that the ice making capacity of the machine is reduced by that much.
Further, even in the case where locking of the machine is prevented by use of a gas thermometer, a gas thermometer typically has a very poor responsiveness, and thus it takes a very long time to make a judgement that freeze-up has occurred. This often resulted in the ice making machine being broken before its operation is successfully stopped. Further, the ice making operation is brought into a complete halt once a freeze-up condition is judged to have occurred, creating a situation where there is no supply of ice until the ice making operation is resumed. Therefore, there was a problem in that the ice making capacity is considerably reduced also in this respect.
The present invention has been devised in order to solve the aforementioned problems. Therefore, an object thereof is to provide an anti-lock system for an auger type ice making machine, which prevents locking of the auger type ice making machine without stopping an ice making operation, that is, while maintaining ice making capacity of the machine.
In order to attaint the above object, according to the present invention, there is provided an auger type ice making machine which comprises: a refrigeration circuit provided with a compressor, a condenser, an expansion valve, and an evaporator; a cylinder having the evaporator wound around its outer peripheral surface; an auger rotatably mounted within the cylinder; a motor for rotationally driving the auger; precursor detecting means for detecting a precursor predictive of locking of the motor occurring due to freeze-up in the evaporator; and a bypass passage for bypassing refrigerant on the high-pressure side of the refrigeration circuit to the low-pressure side, in the case where the precursor detecting means has detected the precursor to locking of the motor.
Further, in order to attain the aforementioned object, according to another aspect of the present invention, there is provided an auger type ice making machine which comprises: a refrigeration circuit provided with a compressor, a condenser, an expansion valve, and an evaporator; a cylinder having the evaporator wound around its outer peripheral surface; an auger mounted rotatably within the cylinder; a motor for rotationally driving the auger; precursor detecting means for detecting a precursor to locking of the motor occurring due to freeze-up in the evaporator; and condenser capacity adjusting means for reducing condensation capacity of the condenser, in the case where the precursor detecting means has detected the precursor to locking of the motor.
Further, in order to attain the aforementioned object, according to yet another aspect of the present invention, there is provided an auger type ice making machine which comprises: a refrigeration circuit provided with a compressor, a condenser, an expansion valve, and an evaporator; a cylinder having the evaporator wound around its outer peripheral surface; an auger rotatably mounted in the cylinder; a motor for rotationally driving the auger; precursor detecting means for detecting a precursor to locking of the motor occurring due to freeze-up in the evaporator; and compressor capacity adjusting means for reducing compression capacity of the compressor, in the case where the precursor detecting means has detected the precursor to locking of the motor.
The precursor detecting means may determine that there exists a precursor to locking of the motor upon detecting one of the following: a drive current of the motor becomes equal to or greater than a threshold; one of an outlet temperature and an outlet pressure of the evaporator becomes equal to or lower than a threshold; and one of an outlet temperature and an outlet pressure of the condenser becomes equal to or lower than a threshold.